/**
 * Copyright(c) 2014 Xunton Solutions
 *
 * History:
 *   15-1-12 下午2:33 Created by dwzhang
 */
package com.jade.framework.base.util;

/**
 * 距离工具类。
 *
 * @author <a href="mailto:dwzhang@xunton.com">dwzhang</a> 
 * @version 1.0 15-1-12 下午2:33
 */
public class DistanceUtils
{
    private static final double EARTH_RADIUS = 6378.137;

    private static double rad(double d)
    {
        return d * Math.PI / 180.0;
    }

    public static double getDistance(double lat1, double lng1, double lat2, double lng2)
    {
        double radLat1 = rad(lat1);
        double radLat2 = rad(lat2);
        double a = radLat1 - radLat2;
        double b = rad(lng1) - rad(lng2);
        double s = 2 * Math.asin(Math.sqrt(Math.pow(Math.sin(a / 2), 2) +
                Math.cos(radLat1) * Math.cos(radLat2) * Math.pow(Math.sin(b / 2), 2)));
        s = s * EARTH_RADIUS;
        return s;
    }

    public static double getLatitude(double distance)
    {
        double d = Math.PI * EARTH_RADIUS / 180;
        return distance / d;
    }

    public static double getLongitude(double latitude, double distance)
    {
        double d = Math.PI * EARTH_RADIUS / 180;
        return distance / Math.abs(Math.cos(Math.toRadians(latitude)) * d);
    }
}